Oxidation resistant lubricants



United States Patent 3,185,643 OXIDATION RESISTANT LUBRICANTS Warren Lowe, Berkeley, and Frank A. Stuart, Oriuda, Califi, assignors to California Research Corporation, San Francisco, Calif., a corporation of Delaware N0 Drawing. Filed Sept. 28, 1962, Ser. No. 227,036 Claims. (Cl. 25232.7)

This invention pertains to lubricating oil compositions havingincorporated therein metal-free detergents. These particular detergents are also effective as oxidation inhibitors.

Present day internal combustion engines operate at high speeds and high compression ratios. When used in the socalled city stop-and-go driving, which includes the greater part of the driving conditions for a large percentage of todays automobiles, the internal combustion engines do not reach the most efiicientoperating temperature. Under city driving conditions, large amounts of partial oxidation products are formed, and reach the crankcase of the engine by blowing past the piston rings. Most of the partial oxidation products are oil-insoluble, tending to form deposits on the various operating parts of the engine, such as the pistons, piston rings, etc. For the purpose of preventing the deposition of these products on the various engine parts, it is necessary to incorporate detergents in the lubricating oil compositions, thus keeping these polymeric products dispersed in a condition unfavorable for deposition on metals.

For the most part, the detergents which are added to crankcase oils to reduce this formation of sludges and varnishes are metal organic compounds, particularly those compounds wherein the metal is linked to an organic group through an oxygen 'atom.- Although these metalcontaining organic compounds have some effectiveness as detergents for dispersing the precursors of the deposits within the oil itself rather than permitting them to form as deposits on the engine parts, they have the disadvantage I of forming ash depositsin the engine. These ash deposits lower engine performance by fouling spark plugs and valves,'and contributing to pre-ignition.

It is a particular object of this invention to provide lubricating oil compositions having incorporated'therein metal-free detergents which are also eifective as oxidation inhibitors. Thus, these new additives inhibit the oxidation of lubricating oil compositions and also disperse the undesirable polymeric products which are formed.

Therefore, in accordance with this invention, it has been found that lubricating oil compositions particularly useful for heavy duty service are obtained by incorporating therein a product obtained by reacting an alkenyl succinic anhydride and a polyalkylene polyamine, followed by reaction with a dihydrocarbyl dithiophosphoric acid to form a salt thereof.

By the use of lubricating oil compositions containing the salts described herein, diesel and gasoline engine prod ucts remain remarkably free of deposits and varnish even under severe operating conditions.

The alkenyl succinic anhydrides which are reactants herein are of the formula:

3,185,643 Patented May 25, 1965 ice and polymers of mixtures of l-butene and isobutene hav= ing from 50 to 200 carbon atoms.

The polyalkylene polyamines, which contribute the imide and the basic nitrogen atoms of the reaction products herein, are derived from polymers of ethylene or propylene, such as polyethylene polyamine, and polypropylene polyamines. Such polyalkylene polyamines may be represented by the formula wherein the R represents the divalent radical ethylene or propylene, and x is a number having a value from 1 to 10 or more. Examples of these polyalkylene polyamines include diethylene triamine, triethylene tetramine, tetraethylene pentamine, pentaethylene hexamine, dipropylene triamine, dipropylene tetramine, tetrapropylene pentarnine, pentapropylene hexamine, di-(trimethylene)- triamine, di(trimethylene)tetramine, tetra-(trimethylene)- pentamine and penta-(trimethylene)hexamine.

The dihydrocarbyl dithiophosphoric acids which are used in the salt formation herein are represented by the formula:

wherein R and R represent hydrocarbon radicals each having from 1 to 25 carbon atoms, preferably from 4m 20 carbon atoms. The R and R combined can have a total of from 6 to 50 carbon atoms, preferably from 10 to 40 carbon atoms.

The R and R radicals are exemplified as follows: methyl, ethyl, propyl, isopropyl, butyl, isobutyl, amyl, sec-amyl, hexyl, isohexyl, n-octyl, n-decyl, n-dodecyl, tetradecyl, octadecyl, cyclohexyl, phenyl, amylphenyl, hexadecylphenyl, etc.

Examples of dihydrocarbyl dithiophosphoric acid include dimethyldithiophosphoric acid, methylethyldith-iophosphoric acid, diethyldithiophosphoric acid, di-n-propyldithiophosphoric acid, diisopropyldithiophosphoric acid, di-n-butyldithiophosphoric acid, diisobutyldithiophosphoric acid, n-butyl-n-amyldithiophosphoric acid, disecamyldithiophosphoric acid, methyl-n-hexyl-dithiophosphoric acid, isobutyl-n-hexyldithiophosphoric acid, di-noctyldithiophosphoric acid, methylcyclohexyl dithiophosphoric acid, methylcyclohexyldithiophosphoric acid,dicyclohexyldithiophosphoric acid, methylphenyldithiophosphoric acid, diphenyldithiophosphor-ic acid, di-(amylphenyDdithiophosphoric acid, di-(hexadecylphenyDdithiophosphoric acid, etc.

The reaction between a polyalkylene polyamine and an alkenyl succinic anhydride can proceed at temperatures ranging from 220 F. to 500 F., preferably from 220 F. to 350 F.

The mol ratio of polyalkylene polyamine to succinic anhydride can vary from 0.5:1 to 1:1. Preferably, the polyamine-anhydride mol ratio is 0.8 to 1.

For purposes of simplicity, the product obtained by the reaction of a polyalkylene polyamine and an alkenyl succinic anhydride will be termed a succinimide.

The succinimides herein are reacted with a dihydrocarbyl dithiophosphoric acid at temperatures such that no hydrogen sulfide is evolved; that is, temperatures insufiicient for hydrogen sulfide formation. Such temperatures are from 50 F. to 220 F., preferably F. to 200 F.

The mol ratio of the succinimide to the dihydrocarbyl dithiophosphoric acid can vary from 1:1 to 1:4.

As identified herein, the term salt means the product obtained by reacting the above-identified succinimide with the described dihydrocarbyl dithi-ophosphoric acid.

Examples of such salts include the dimethyl dithiophosphoric acid salt of N-(triethylene tetraminoethyl) octadecenyl succinimide, the isobutyl-n-hexyl dithiophosphoric acid salt of N-(d-iethylene triaminoethyl)hexacontenyl succinimide, the cyclohexyl phenyl dithiophosphoric acid salt of N-(ethylene diaminoethyl)hexatonenyl (C succinimide, and the diphenyl dithiophosphoric acid salt of N-(tripropylene tetraminoethyl)pentacontenyl succinimide.

Lubricating oils which can be used as base oils include a wide variety of lubricating oils, such as naphthenic base, paraffin base, and mixed base lubricating oils, other hydrocarbon lubricants, e.g., lubricating oils derived from coal products, and synthetic oils, e.g., alkylene polymers (such as polymers of propylene, butylene, etc., and the mixtures thereof), alkylene oxide-type polymers (e.g., propylene oxide polymers) and derivatives, including alkylene oxide polymers prepared by polymerizing the alkylene oxide in the presence of water or alcohols, e.g., ethyl alcohol, dicarboxylic acid esters (such as those which are prepared by esterifying such dicarboxylic acids as adipic acid, azelaic acid, sirberic acid, sebacic acid, alkanol succinic acid, fumaric acid, maleic acid, etc., with alcohols such as butyl alcohol, hexyl alcohol, Z-ethylhexyl alcohol, dodecyl alcohol, etc.), liquid esters of acids of phosphorus, alkyl benzenes (e.g., monoalkylbenzene such as dodecyl benzene, tetradecyl benzene, etc.), and dialkyl benzenes (e.g., n-nonyl Z-ethyl hexyl benzene); polyphenyls (e.g., biphenyls and terphenyls), alkyl biphenyl ethers, polymers of silicon (e.g., tetraethyl silicate, tetraisopropyl silicates, tetra(4-rnethyl-2-pentoxy)disiloxane, poly(methyl)siloxane, poly(methylphenyl)siloxane, etc.). Synthetic oils of the alkylene oxide-type polymers which may be used include those exemplified by the alkylene oxide polymers.

The above base oils may be used individually or in combinations thereof, wherever miscible or wherever made so by the use of mutual solvents.

The succinimide-dithiophosphoric acid salt can be used in oils of lubricating viscosity in amounts of 0.10% to 40%, by Weight, preferably 0.1% to 15% by weight; more preferably 1% to The reaction of an alkenyl succinirnide with a polyalkylene polyamine is illustrated in the following example.

EXAMPLE I Reaction product of tetraethylene pemamine and. polybutenyl succinic anhydride A mixture of '84 grams (0.45 mol) of tetraethylene pentamine and 702 grams (0.45 mol) of a polybutenyl succinic anhydride wherein the polybutenyl radical was derived from a polyisobutene having a molecular Weight of about 1,000, was blended with agitation at 125 F. in a nitrogen atmosphere. The temperature was increased to 400 F. during a period of one hour, after which the absolute pressure was reduced to about 200 mm. Hg during a period of 30 minutes to facilitate the removal of water. The reaction mixture was then allowed to reach room temperature at this reduced pressure. The reaction product contained 5.1% nitrogen.

Table I hereinbelow presents further data on the effectiveness of the reaction products described herein as lubricating oil additives. The data of Table I were obtained under the severe conditions of a Caterpillar engine test under the Mil L45199 procedure. This Military specification procedure is so severe that the engine will not even operate with a base oil uncompounded. Even a base oil with the normal commercial additives under this procedure does not provide suificient lubrication; that is, the engine itself eventually sticks.

The lubricating oil composition used in obtaining data for Table I consisted of the base oil having incorporated therein a product obtained by first reacting a polyisobutenyl succinic anhydride, wherein the polyisobutenyl pentamine in a 1:1 mol ratio as in Example I hereinabove, and the resulting imide was reacted with a di(alkylphenyl) dithiophosphoric acid wherein the alkyl radical was a polypropylene containing an average of about 13 carbon atoms. The succinirnide/dithiophosphoric acid mol ratio was 1:1. The amount of additive was equivalent to 10% by weight of the irnide.

The PD Nos. refer to the piston discoloration rating. After the engine test, the three piston lands are examined visually. To a piston skirt which is completely black is assigned a PD No. of 800; to one which is completely clean, a PD No. of 0; to those intermediate between those completely black and completely clean are assigned PD Nos. intermediate in proportion to the extent and degree of darkening.

The GD Nos. refer to the percentage deposit in the piston ring grooves; that is, a 0 evaluation being a clean groove, and a evaluation being a groove full of deposits.

The base oil was a California paraffin-ic base oil having a viscosity of 500 SSU at 100 F.

TABLE I Test results hours):

GD No. 51 PD Nos.--

Land 550, 200, 15, 0 Skirt 0 Table II hereinbelow presents data obtained from the L4 strip test, which is designed to evaluate the bearing corrosion characteristics of lubricating oil compositions. This test was run by immersing a copper-lead strip in the oil being tested for 20 hours at 340 F. The numbers in Table 11 represent the weight loss in milligrams.

The base oil was a California paraflinic base oil having a viscosity of about 500 SSU at 100 F.

Additive A was an alkenyl succinimide of tetraethylene pentamine wherein the alkenyl radical contained 66 carbon atoms.

Additive B was the salt obtained by reacting 1 mol of the alkenyl succinimide of tetraethylene pentamine with 1 mol of an alkylphenyl dithiophosphoric acid, wherein the alkyl radical was derived from a propylene polymer having an average of from 12 to 14 carbon atoms.

Adidtive C was the above-described alkylphenyl (lithiophosphoric acid.

TABLE II Mel Ratios, Composition Dithiophos- L-4 Test phoric Acid/ Result Succinimide 1. Base oil 2.8% wt. Additive A 1% wt.

Additive O 0. 36:1 52. 3 2. Base Oil 1.35% wt. Additive A 1% 7 wt. Additive C 0.75:1 67. 9 3. Base oil 3% wt. Additive B 1:1 4. 2

TABLE III Copper Lead Table IV presents data obtained in a Caterpillar L-1 test, 120 hours.

The base oil was a California solvent-refined SAE 30 base oil containing in amount of 1. 35% by weight, a product which was obtained by reacting a polyisobutenyl succinic anhydride with tetraethylene pentam-ine as in Example I hereinabove, and the resulting succinimide reacted with the above-described di(alylphenyl)dithiophosphoric acid. The succinirnide-dithiophosphoric acid mol ratio was about 1:1.

The efiectiveness of the additives described herein in reducing bearing corrosion was further determined by evaluating a lubricating oil composition in an L38 test, using a 1 cylinder CLR engine in a test period of 40 hours. The lubricating oil composition consisted of a Mid- Continent SAE 30 base oil containing 2.26% by Weight of a product obtained by 1) reacting an alkenyl succinic anhydride and tetraethylene pentamine as in Example I, followed by (2) reacting the product of (1) with a dialkyl dithiophosphoric acid in a 1:1 mol ratio, wherein one alkyl radical contained 4 carbon atoms, and the second alkyl radical contained 5 carbon atoms.

The bearing weight loss was only 67 mgs., as opposed to a weight loss of 5099 mgs. when using 3% by weight of the succinimide itself.

We claim:

1. A lubricating oil composition comprising a major proportion of an oil of lubricating viscosity and from 0.-'1% to 40% by weight, of a product obtained by (1) reacting an alkenyl succinic anhydride having from 50 to 200 carbon atoms in the alkenyl radical with a polyalkylene polyamine of the formula NH R(NHR) NH wherein R is a divalent radical selected from the group consisting of ethylene and propylene and x is a number having a value from 1 to 10, wherein the polyamine-anhydried mol ratio is from 0.5:1 to 1:1, followed by (2) reacting the product of (1) with dihydrocarbyl dithiophosphoric acid of the formula wherein R and R are hydrocarbon radicals each having from 4 to 20 carbon atoms and having a combined number of carbon atoms from 10 to 40, wherein the mol ratio of the product of (1) to dithiophosphoric acid is from 1:1 to 1:4, said reaction (1) being carried out by heating at a temperature from about 220 F. to about 550 F., and said reaction (2) being carried out by heating at a temperature from about F. .to about 200 F.

2. A lubricating oil composition comprising the composition of claim "1 in which the polyalkylene polyamine is tetraethylene pentamine and the dihydrocarbyl dithiophosphoric acid is alkylphenyl dithiophosphoric acid.

3. A lubricating oil composition comprising the composition of claim 1 in which the polyalkylene polyamine is tetraethylene pentamine and the dihydrocarbyl dithiophosphoric acid is dialkyl dithiophosphoric acid.

4. A lubricating oil composition comprisin the composition of claim 1 in which the polyalkylene polyamine is diethy-lene triamine and the dihydrocarbyl dithiophosphoric acid is alkyphenyl dithiophosphoric acid.

5. A lubricating oil composition comprising a major proportion of an oil of lubricating viscosity and from 1% to 10% by weight of a product obtained by (1) reacting at 220 F. to 500 F. an alkenyl succinic anhydride having from 50 to 200 carbon atoms in the alkenyl radical with tetraethylene pentamine wherein the tetraethylene pentamine-anhydride mol ratio is from 0.5 :1 to 1:1 followed by (2) reacting the product of 1) at 150 F. to about 200 F. with a dihydrocarbyl dithiophosphoric acid of the formula References Cited by the Examiner UNITED STATES PATENTS 2,809,934 10/57 Alford et a1. 25232.7 2,973,323 2/61 Millikan et a1. 25232.7 2,995,568 8/61 Malz et a1. 260326.5 3,018,247 1/62 Anderson et a1. 252-327 3,058,910 10 /62 Clumer 252 32.7 3,074,990 1/63 Cyba 25232.7

DANIEL E. WYMAN, Primary Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,185,643 May 25, 1965 Warren Lowe et a1.

It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 2, lines 24 to 29, the formula should appear as shown below instead of as in the patent:

R-O-P-SH column 4, line 46, for "Adidtive" read Additive column 5, line 8, for "di(aly1phenyl)" read di[alkylphenyl) lines 43 and 44, for "-anhydried" read ---anhydride column 6, line 5, for "550 F." read 500 F. line 19, for "alkyphenyl" read alkylphenyl Signed and sealed this 7th day of December 1965.

(SEAL) Attest:

ERNEST W. SWIDER EDWARD J. BRENNER Attesting Officer Commissioner of Patents 

1. A LUBRICATING OIL COMPOSITION COMPRISING A MAJOR PROPORTION OF AN OIL OF LUBRICATING VISCOSITY AND FROM 0.1% TO 40% BY WEIGHT, OF A PRODUCT OBTAINED BY (1) REACTING AN ALKENYL SUCCINIC ANHYDRIDE HAVING FROM 50 TO 200 CARBON ATOMS IN THE ALKENYL RADICAL WITH A POLYALKYLENE POLYAMINE OF THE FORMULA 